Generally, a vehicle is provided with a system configured to supplement vehicle braking with downshifting of a transmission gear position to assist in slowing down the vehicle during vehicle travel along a declining road grade. This system is configured to calculate road grade and to determine brake application prior to initializing engine braking. In one system, to determine the road grade encountered by a vehicle, vehicle conditions (i.e., vehicle acceleration, accelerator pedal depression, or the like) are monitored and provided to an electronic controller (“EC”). Likewise in the same system, to determine the application of a brake, vehicle conditions such as brake pedal application, absence of accelerator pedal depression, or the like are monitored and provided to the EC. When the monitored conditions indicate a declining road grade and brake pedal application, the EC will initiate downshifting to slow down the vehicle.
Such systems, however, may have problems whereby downshifting is not initiated when brakes are applied during road grade decline. For instance, the EC may discontinue road grade calculation during the application of the brake pedal to prevent erroneous road grade calculations. Repeated brake application may continuously discontinue road calculations and may not provide sufficient time subsequent to each brake application to accurately calculate road grade. Therefore, declining road grade may not be indicated during brake application and downshifting may not be initiated appropriately. Accordingly, there is a need to more accurately initiate downshifting when a vehicle brakes along a decline.